json.Number is not serialized as Int type

It will be very convinient to use json.Number when buillding the response, right now it is not possible,
as Int serializer does not encount it.

Start by locating the Int serializer and checking how Go's json.Number is represented and validated. Confirm the expected GraphQL response behavior, then add or update coverage showing that json.Number is accepted and serialized as an Int.

Written by the indexing model from the issue text.